A growing proportion of the population in the industrialized world spends time performing tasks that are known to cause eye fatigue and/or eye strain. Office workers increasingly are required to work at computer terminals to perform tasks such as word processing, data entry, and generating computer graphics. Students and children are using computers for study and in the classroom. Even at home, computers and televisions are commonly viewed for entertainment and information purposes. Thus, it comes as no surprise that an increasing number of people in the industrialized world are seeking relief from discomfort and decreased vision due to eye strain.
The human eye includes various muscles which, like any part of the human body, will tire and strain when kept in a fixed configuration for sufficiently long periods. Immediate symptoms of eye fatigue and eye strain include headaches and difficulty focusing one's vision. In the long term, prolonged or severe eye fatigue and strain may decrease the strength of eye muscles and require corrective lenses (or an increased prescription for those already requiring corrective lenses).
Some of the most common causes of eye fatigue and/or strain include viewing close objects, viewing objects displayed on a light emitting medium, and simply viewing images for excessive time periods. By way of example, a typical computer user may spend hours viewing a computer display screen while performing computer-related tasks. The light emitting display screen forces the computer user's eyes to constantly adjust, while simultaneously diminishing the eyes movement which normally helps the eyes to stretch and relax and thereby relieve eye fatigue and eye strain. Furthermore, objects being viewed on the display screen are often close enough to the viewer to cause the viewer's eye difficulty in maintaining a clear focus on the objects, possibly causing eye strain and fatigue. As will be appreciated, the effects of such causes on a particular viewer vary depending upon the visual abilities of that particular viewer.
When an object is too close to a viewer, the viewer is forced to bring her eyes inward (towards her nose). The motion of the eyes turning inward is called convergence. Convergence requires intensive exertion of the eye muscles, in particular the ocular muscles. When the eyes are not properly relaxed through either visual exercise or rest, the viewer may experience eye fatigue and/or eye strain. Repeated and/or prolonged convergence can permanently decrease the strength of the eye muscles.
In addition, a viewer's eyes must focus in order to properly perceive an object. Focusing causes strain to the viewer's eyes. In order to focus on close objects, the eye's lens thickens. That is, the closer an object to the viewer, the thicker the eye's lens must shape themselves. Thickening the eye's lens is particularly exhausting on the eye muscles, serving to exacerbate the fatigue and strain brought on by the convergence that also accompanies viewing close objects.
One result of eye fatigue and eye strain is a diminished synchronization between a viewer's pair of eyes. That is, the viewer's left and right eyes are not working synchronously to provide the visual information required to visually perceive one's surroundings. Accordingly, common orthoptic tests involve monitoring the eye's ability to synchronize, while common orthoptic treatments involve the viewer performing eye exercises that promote synchronization, either through stretching and strengthening the eye muscles, or via forced relaxation.
FIG. 1 illustrates an orthoptical exercise method 100 commonly performed with a synoptophore by optometrists (or other medical professionals), together with their patients, to examine and promote eye synchronization. The method 100 begins in a step 102 involving any initialization requirements. These depend, in part, upon the equipment being used. However, in general, a viewer (i.e., the patient) places their face over the viewing portion of eye synchronization test equipment such that each eye is looking into an individual scope. Once the viewer is prepared, a step 104 displays two associated images, one in each scope. Typically, the two associated images are not identical, but have many common portions. After the two associated images are displayed, in a step 106 the viewer focuses the two images into a single perceived "merged" image. In general, the merged image is a mapping of the two associated images. In a simple case, the single perceived merged image will replicate all the common portions of the associated images, as well as each of the associated images' unique portions. An example of a single perceived merged image of this type is described below in reference to FIGS. 2(b) and 2(c). In other cases, however, the single perceived image might replicate all the common portions but create a portion perceived as three dimensional out of the associated images' unique portions. This is due to the operation of the viewer's eyes intended to provide stereoscopic vision. As will be appreciated, "stereoscopic vision" is the ability to perceive distance and the three dimensional properties of a viewed object.
Once the viewer has focused on a single perceived merged image, it is determined in a step 108 whether the method 100 is done. For example, has the viewer completed his or her exercises, or has the optometrist completed the tests? If so, then the method is complete in a step 110. If the method 100 is not complete, then step 108 passes control to a step 112. In a step 112, the optometrist manually adjusts the two associated images along the horizontal plane, disrupting the viewer's focus and thereby causing the viewer to once again perceive the two associated images as distinct and not one single perceived merged image. After step 112, the method 100 loops back to step 106 where, once again, the viewer is allowed to focus the two images into a single perceived merged image.
FIG. 2(a) illustrates a patient 136 utilizing a synoptophore 140 suitable for performing the method 100 of FIG. 1. The synoptophore includes a left scope 126 and a right scope 128 coupled with a viewing screen 142. The patient 136 places her face up against the synoptophore 140 such that the patient's left and right eyes are directly in front of the left scope 126 and the right scope 128, respectively. Two associated images, such as those described above with reference to FIG. 1, are displayed by the viewing screen 142, one in each scope. As described above, the patient 136 then focuses her eyes to perceive a single, merged image.
With reference now to FIGS. 2(b) and 2(c), a specific example of two associated stick house images 120 and 122 along with a perceived merged image 124 will be described. Broken lines represent the left scope 126 and right scope 128 of the synoptophore 140 described above with reference to FIG. 2(a). Thus, a viewer gazing only into the left scope 126 would perceive just the image 120. Similarly, a viewer gazing only into the right scope 128 would perceive just the image 122. However, a viewer gazing into both scopes appropriately would initially see both images, as described above with reference to steps 104 and 106 of FIG. 1. Then, as described above with reference to step 106 of FIG. 1, the viewer would begin to focus and shortly thereafter perceive just the single merged image 124 of FIG. 2(b). Note that a chimney portion 130, only presented in the image 120, and a doorway portion 132, only presented in the image 132, are both perceived by the viewer in the single perceived merged image 124.
While the method 100 is useful in testing and promoting eye synchronization, it has a number of drawbacks. For example, imprecise operation by the optometrist decreases the effectiveness that the method 100 has upon eye strain and fatigue. Flaws such as asynchronous movement of the associated images, including substantially discrete jumps and differing average speeds, serve to prevent the patient from obtaining the optimal benefit. In addition, these methods must be performed in a doctor's office or with the aid of equipment and assistance that are not easily provided in the very environments where the eye strain and eye fatigue is being experienced. Thus, sufferers of eye strain and fatigue must travel to doctors' offices for expensive and lengthy treatments.
It would be advantageous to provide methods and systems that overcome the above-described drawbacks with current treatments for eye strain and eye fatigue. In particular, it would be advantageous to provide systems and methods that provide highly synchronized, smooth motion of images for eye training. In addition, it would be advantageous to provide systems and methods for treating and/or preventing eye strain and eye fatigue that can be performed locally and without extensive apparatus or manual assistance.